Nonenzymatic amperometric sensor for hydrogen peroxide released from living cancer cells based on hierarchical NiCoO-CoNiO hybrids embedded in partially reduced graphene oxide.

The synthesis of hierarchical NiCoO-CoNiO hybrids embedded in partially reduced graphene oxide (represented by NiCoO/CoNiO@pPRGO) is described. They were derived from ultrathin CoNi-based zeolitic imidazolate framework (CoNi-ZIF) nanosheets vertically grew on three-dimensional (3D) pRGO networks by pyrolysis at different temperatures (300, 600, and 900 °C) in N atmosphere. Transmission electron microscopy, X-ray diffraction, and X-ray photoemission spectroscopy measurements showed that the metal coordination centers (Co or Ni) were transferred into NiCoO spinel and CoNiO nanostructures, along with a small number of metallic states of Co and Ni. In view of good electrochemical conductivity and large specific surface area of pRGO, good catalytic activity of Co- and Ni-contained NPs, and homogeneous distribution of NPs within the pRGO network, the NiCoO/CoNiO@pRGO nanohybrid calcined at 600 °C displayed superior electrocatalytic activity toward hydrogen peroxide (HO) reduction. A glassy carbon electrode modified with NiCoO/CoNiO@pRGO was used for determination of HO by amperometry at an applied potential of - 0.4 V vs. Ag/AgCl. The nonenzymatic amperometric sensor exhibited high sensitivity and low detection limit (0.41 μM) within a wide working range (5 μM-3 mM and 3-12 mM) toward HO, as well as good selectivity, reproducibility, and long-term stability. Benefiting from the good biocompatibility and remarkable analytical performances of NiCoO/CoNiO@pRGO, the assay was used to determine real-time HO released from living cancer cells. Graphical abstract.